1. Field of the Invention
This invention relates to fuel cells, and more particularly to fuel cells capable of favorably measuring partial voltages within a stack of the fuel cells.
2. Description of the Related Art
A fuel cell is generally known in which a membrane electrode assembly formed by integrating an electrolyte membrane with electrode catalyst layers, or the like, and separators are laminated or stacked together. In this type of fuel cell, a set of separators may be composed of two or more separator components (which will be hereinafter called “plates”). For example, a membrane electrode assembly is sandwiched between two plates, i.e., a cathode-side plate and an anode-side plate, to form a unit cell, and a plurality of unit cells are stacked together to provide a fuel cell stack, as disclosed in Japanese Patent Application Publication No. 2001-256992 (JP-A-2001-256992). In this fuel cell structure, two plates are present between the adjacent membrane electrode assemblies, and these two plates provide a set of separators. In the following description, the set of separators composed of two or more plates may be regarded as “separator assembly”. As another example, Japanese Patent Application Publication No. 4-267062 (JP-A-04-267062) discloses a separator assembly composed of three metal plates.
In the fuel cell stack, terminals for detecting voltage may be provided on the separators, so as to monitor the power generation status in each of the membrane electrode assemblies. For example, it is disclosed in JP-A-2001-256992 that a terminal for measuring voltage is attached to the corresponding separator assembly such that two plates of the separator assembly are gripped by the terminal.
In the separator assembly consisting of two or more plates, however, external force or vibrations may cause the plates to be displaced relative to each other. Therefore, if a terminal for measuring voltage is connected to the separator assembly, force may be applied to the terminal due to displacement of the plate(s), and the terminal may deform or fall off. In this case, voltage may not be measured with accuracy.